Many vehicle emissions control systems include an evaporative canister, or EVAP canister configured to absorb fuel vapors from the fuel tank during some engine operational modes, such as when the engine is off, and/or during refueling. Typically the EVAP canister is fluidically coupled with the fuel tank and has an internal surface coated with a substance, such as activated charcoal, effective at absorbing the vapors. The canister may be purged during other engine operational modes in order to make the absorbing surfaces available to absorb more fuel vapor. During purge operations the vacuum pressure of the intake manifold is used to pull atmospheric air through the canister and into the engine combustion chamber.
The inventors herein have recognized that some engine technologies, for example newer, and/or proposed technologies, may run at low vacuum or near atmosphere pressure as measured post throttle body in the engine's intake manifold. This may result in insufficient air flow to sufficiently purge the hydrocarbons that are stored in a conventional evaporative system and carbon canister. U.S. Pat. No. 6,695,895 also recognizes the potential shortcomings presented by low intake manifold vacuum. The disclosure proposes to make up for insufficient negative pressure in the intake pipe by providing a purge pump on an atmospheric port side or on a purge port side, and increasing the pressure at the side of the atmospheric port of the canister or increasing the negative pressure at the side of the purge port so as to accelerate the supply of air into the canister.
The inventors herein have recognized a number of problems with this approach. For example, the approach requires adding a pump and thereby adding additional cost and complexity to the engine.
The present disclosure has at least partially addressed these problems, and provides additional advantages. The present disclosure may provide a purge valve for use in a fuel combustion engine. The purge valve may include a first inlet for coupling with an air cleaner to receive a first flow from the air cleaner, and a second inlet for coupling with an evaporative canister to receive a second flow from the evaporative canister. The purge valve may have an outlet that may be fluidically coupled to an upstream side of a throttle providing a fluid path to a combustion chamber of the engine. A controller may be configured to selectively control relative amounts of the first flow and the second flow which are allowed to pass through the outlet and to the combustion chamber.
The present disclosure may also provide a valve for an engine. The valve may have a first inlet for receiving atmospheric air as a first flow, and a second inlet for receiving a purge flow from an evaporative canister as a second flow. The evaporative canister may be fluidically coupled with a fuel tank and may be configured for absorbing fuel vapor. The purge flow may include desorbed fuel vapor. The valve may also have an outlet for directing a selected mixture of the first flow and the second flow to a combustion chamber of the engine. In some cases the outlet may be coupled with an induction air passage upstream from a throttle. In some cases the outlet may be coupled with an induction air passage upstream from a turbo compressor.
The present disclosure may also provide a fuel vapor management system for an engine. The fuel vapor management system may include an evaporative canister including a fuel vapor absorbing material. The system may also include a turbo compressor on an induction air path for compressing an induction fluid before the induction fluid is passed to an intake manifold of the engine. A valve may be located on the induction air path upstream from the turbo compressor, and may have a first inlet to receive a first flow, and having a second inlet to receive a second flow from the evaporative canister. The valve may be controllable to adjust relative amounts of the first flow and the second flow to pass to the turbo compressor.
In this way even in conditions of low vacuum within the intake manifold, a sufficient pressure differential may be obtained across the evaporative canister. In this way, effective purging of the absorbed fuel vapors may be achieved.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.